1. Technical Field
This invention relates generally to a method for improving the efficiency obtained in the burning of a heavy fuel oil in a boiler or other combustion device and to methods and means for preparing the fuel oil for combustion.
More specifically, this invention relates to a method for improving the combustion efficiency of a heavy fuel oil by mixing an effective amount of a combustion enhancing material comprising a high molecular weight, viscoelastic polymer to a heated fuel oil just prior to its combustion.
This invention further relates to a means for producing a homogeneous mixture of a heavy fuel oil and a viscoelastic polymer without degradation of the polymer or interfering with normal operations of the combustion device
2. Description of Related Art
It is well known that the addition of a low concentration of a long chain, high molecular weight, hydrocarbon polymer to a liquid hydrocarbon can result in significant changes to the flow behavior of the resulting solution. If the hydrocarbon polymer has a sufficiently high molecular weight, of at least about 2.5 million daltons, then the resulting solution will exhibit viscoelasticity, displaying both viscous and elastic characteristics when undergoing rapid flow or other deformation. Low concentrations of relatively high molecular weight polymers, particularly such polymers as polyisobutylene, are known to reduce turbulence and have been used as drag reducing agents in pipelines, see for example, U.S. Pat. No. 4,837,249. These same polymers are also known to impart anti-misting properties to jet fuels to reduce flammability of fuel sprays occurring during aircraft crashes, see for example, U.S. Pat. No. 4,789,383.
High molecular weight hydrocarbon polymers, especially those substantially linear polymers such as polyisobutylene, have also found use as a fuel modifying agent for gasoline and diesel engines. As is described in U.S. Pat. No. 5,906,665, a high molecular weight polyisobutylene is first dissolved by extended gentle stirring in a petroleum solvent such as isooctane to obtain a stock solution containing about 2% polyisobutylene. That stock solution can then added directly at the time of refueling to the fuel tank of a vehicle where it readily dissolves. Substantial improvements in fuel consumption and acceleration were observed.
The effect of adding a high molecular weight hydrocarbon polymer, in this case polyisobutylene, on diesel engine performance was also extensively tested and the results reported in SAE Publication No. 2007-01-3981. As reported in that paper, the addition of about 5 ppm of the polyisobutylene agent to the fuel burned in several different commercial (Cummins, Caterpillar and Detroit) diesel engines resulted in a reduction in exhaust particulate matter on the order of 20% to 50% while also reducing NOx on the order of 5% to 25%. In some cases, fuel economy was also improved upon use of the polymer additive.
Attempts have also been made to improve the combustion efficiency of stationary industrial boilers burning heavy fuel oils by adding polymeric fuel modifying agents to the heavy fuel oil prior to combustion. Those attempts have met with failure in that no measurable increase in combustion efficiency could be observed.
This invention provides a technique for successfully employing a polymer additive to increase the combustion efficiency of a boiler or other combustion device burning heavy fuel oils and provides means for practicing that technique.
Other features and advantages of this invention are set out in the following description of the presently preferred embodiments of the invention.